Go into Apps. Do a long touch on the app in question. Select Optimize App from the dropdwon list of options. Uncheck the "Always use in full screen" box.

In most apps, that will allow the Onyx task bar to be seen at the top of the screen. However, for a few apps, that doesn't seem to work. They always seem to use the full screen regardless of whether or not the box is unchecked. Not sure why.